WORKING FOR A HEALTHY FUTURE

INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org

Estimation of the Burden of Cancer in Great Britain due to Occupation

L Rushton1, T. Brown2, R Bevan3, J W Cherrie4, G Evans2, L Fortunato1, S Bagga3, P Holmes3, S Hutchings1, R Slack3, M Van Tongeren4, C Young2

1 Dept. of Epidemiology and Biostatistics, Imperial College London; 2 Health and Safety Laboratory, Buxton, Derbyshire3 Institute of Environment and Health, Cranfield University4 Institute of Occupational Medicine

This study was funded by the Health and Safety Executive

Aims of the study…

Current Burden of Occupational Cancer:• to develop and apply methodology to estimate current

attributable risk, cancer numbers and DALYs caused by work• to identify important cancer sites• to identify industries and occupations for targeting for reduction

measures

Prediction of Future Burden of Occupational Cancer:• Estimate size of future burden based on current and past

exposures• Identify cancer sites, carcinogens and industry sectors where the

burden is greatest• Demonstrate effects of measures to reduce exposure

Current Burden Methodology…

• Attributable fraction (AF): the proportion of cases due to occupation Requires:• Risk of Disease (relative risk estimates from published literature)

• Proportion of Population Exposed (derived from national data sources, accounting for employment turnover and life expectancy; adjusted for employment trends)

• Define period of relevant exposure: Risk Exposure Period (REP) based on cancer latency

• Dose-response risk estimates and proportions ever exposed over the REP at different exposure levels not generally available; data therefore obtained for ‘higher’ and ‘lower’ levels

• AFs used to calculate attributable numbers (ANs)

• Estimation for IARC groups 1 (definite) and 2A (probable) carcinogens and occupational circumstances

Cancer Site AF (%) Deaths (2005) Registrations (2004)

M F Total M F Total M F Total

Mesothelioma 97.0 82.5 94.9 1699 238 1937 1699 238 1937

Sinonasal 43.3 19.8 32.7 27 10 38 195 31 126

Lung 21.1 5.3 14.5 4020 725 4745 4627 815 5442

Nasopharynx 10.8 2.4 8.0 7 1 8 14 1 15

Bladder 7.1 1.9 5.3 215 30 245 496 54 550

Breast 4.6 4.6 555 555 1969 1969

NMSC 6.9 1.1 4.5 20 2 23 2513 349 2862

Larynx 2.9 1.6 2.6 17 3 20 50 6 56

Oesophagus 3.3 1.1 2.5 156 28 184 159 29 188

STS 3.4 1.1 2.4 11 3 13 22 4 27

Stomach 3.0 0.3 1.9 101 6 108 149 9 157

NHL 2.1 1.1 1.7 43 14 57 102 39 140

Melanoma (eye)

2.9 0.4 1.6 1 0 1 6 1 6

Total 8.2 (7.2, 9.9)

2.3 (1.7, 3.2)

5.3 (4.6, 6.6)

6355 (5640, 7690)

1655 (1249, 2287)

8010 (6888, 9977)

9988 (6938,

14794)

3611 (2370, 5412)

13598 (9308,

20206)

Carcinogen or OccupationTotal Registrations (% of total burden)

Cancer Sites

Asbestos 4216 (30.8%) Larynx, Lung, Mesothelioma, Stomach

Shift work (+ Flight Personnel) 1957 (14.3%) Breast

Mineral oils 1730 Bladder, Lung, NMSC, Sinonasal

Solar radiation 1541 (11.3%) NMSC

Silica 907 (6.6%) Lung

Diesel engine exhaust 801 (5.9%) Bladder, Lung

PAHs - Coal tars and pitches 545 (4.0%) NMSC

Painters 359 (3.2%) Bladder, Lung, Stomach

Dioxins 316 (2.3%) Lung, NHL, STS

Environmental Tobacco Smoke (non-smokers)

284 (2.1%)Lung

Radon 209 (1.5%) Lung

Welders 175 (1.3%) Lung, Melanoma (eye)

Tetrachloroethylene 164 (1.2%) Cervix, NHL, Oesophagus

Arsenic 129 (0.9%) Lung

Strong inorganic-acid mists 122 (0.9%) Larynx, Lung

Chromium 89 Lung, Sinonasal

Non-arsenical insecticides 73 Brain, Leukaemia, Multiple myeloma, NHL

Industry SectorAttributable Registrations

Male Female TotalExposures

Construction 4573 64 4637 14

Painter + decorators 331 3 334 1

Roadmen + roofers 471 0 471 1

Total construction 5375 68 5442 16

Shift work (including flight personnel) 0 1969 1969 1

Metal workers 1083 169 1252 1

Personal + household services 256 403 659 17

Land Transport 454 42 497 9

Mining 283 12 296 10

Printing, publishing and allied trades 232 50 282 10

Public administration and defence 229 34 263 6

Wholesale + retail trades 51 136 187 11

Farming 180 39 220 5

Welders 165 16 181 2

Manufacture of instruments, etc 204 2 206 6

Manufacture of transport equipment 164 18 182 16

Non-ferrous metal basic industries 122 34 156 18

Predicting Future Burden…

• AFs estimated for forecast years, e.g. 2010, 2020 … 2060

• Define the risk exposure period (REP) for each year e.g. for 2030, 1981 – 2020 (10-50 years latency assumed for solid tumours e.g. lung cancer, 0-20 years for leukaemia)

• Some past and some future exposure until 2060 • Workers at the beginning (2010) assumed to be of all

working ages• Workers recruited through employment turnover are

assumed to be only aged 15-24• Factors stay the same as 2004/5

Predicting future burden…

• Use 4 levels of exposure High/Medium/Low/Background• Method effectively shifts the proportion of workers exposed

in different exposure level categories (H/M/L/B) across time as exposures gradually decrease

• Forecasted numbers take into account employment turnover and employment trends

• Methods applied to top 14 carcinogens/occupations identified as accounting for 85.7% of total current (2004) cancer registrations

• Forecast GB total cancers (deaths and registrations) based ONLY on demographic projections (ONS) and assuming all non-occupational risk

20602020

1971-80 2001-101981-90 1991-00

REPs FTYs20502030 2040

2021-302011-20 2031-40 2041-50

2010

1961-70

10 year estimation intervals

‘Known’ exposure Forecast exposure

Forecast Risk Exposure Periods – 10-50 year latency

REP Risk exposure periodFTY Forecast target year

Change in future exposure: Scenarios

Estimates made for alternative scenarios of changes in exposure levels and/or numbers exposed

• (1) Baseline scenario - based on pattern of past exposure, but no future change in exposed numbers or exposure levels

• (2) Baseline trend scenario - based on pattern of past and current exposure, and on linear projections up to 20 years into the future, after which levels assumed constant due to prediction uncertainty.

• (3) ‘Intervention scenarios’ also based on past and current exposures, and suitably chosen target exposure levels in the future

Change in future exposure: Interventions

Can test:• Introduction of a range of possible OELs or reduction of

a current limit• Improved compliance to an existing exposure standard• Planned intervention such as engineering controls or

introduction of personal protective equipment• Industry closure

Also can vary:• Timing of introduction (2010, 2020 etc)• Compliance levels e.g. according to workplace size (self-

employed, 1-49, 50-249, 250+ employees)

Forecast lung cancers for Respirable Crystalline Silica

2010

Attributable Fraction

Attributable registrations

Avoided registrations

3.3 803

2060

Base-line: exposure limit 0.1mg/m3, compliance 33%

1.08 794

Exposure limit 0.05 mg/m3, compliance 33% 0.80 592 202

Exposure limit 0.025 mg/m3, compliance 33% 0.56 409 385

Exposure limit 0.1 mg/m3, compliance 90% 0.14 102 693

Exposure limit 0.05 mg/m3, compliance 90% 0.07 49 745

Exposure limit 0.025 mg/m3, compliance 90% 0.03 21 773

0

100

200

300

400

500

600

700

800

900

1,000

2010 2020 2030 2040 2050 2060 2070 2080

Attr

ibu

tab

le R

eg

istr

atio

ns

Forecast Year

A)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

2010 2020 2030 2040 2050 2060 2070 2080

Attr

ibu

tab

le F

ract

ion

, %

Forecast Year

B)Attributable registrations

AFs

(1) Baseline: exposure limit 0.1mg/m3 maintained, compliance 33%

(2) Exposure limit 0.05mg/m3 from 2010, compliance 33%

(10) Exposure limit 0.025mg/m3 from 2010, compliance 33%

(11) Exposure limit 0.1mg/m3 maintained, compliance 90%

(12) Exposure limit 0.05mg/m3 from 2010, compliance 90%

(13) Exposure limit 0.025mg/m3 from 2010, compliance 90%

Improvement in compliance by workplace size for Respirable Crystalline Silica

2010

Attributable Fraction %

Attributable registrations

Avoided registrations

3.3 803

2060

Base-line: exposure limit 0.1mg/m3, compliance 33%

1.08 794

Exposure limit 0.05mg/m3, compliance 33% 0.80 592 202

Exposure limit 0.05mg/m3, % compliance changes by employed workplace size and self employed

33% < 250, self employed; 90% 250+ 0.68 499 295

33% < 50, self employed; 90% 50+ 0.61 451 344

33% self employed; 90% all sizes employed 0.35 261 533

90% all workplaces 0.07 49 745

Attributable Numbers of Cancer Registrations

Scenarios

All Base (1) Trend (2) (3) (4) (5) (6)

Exposure Cancer Site 2010 2060

Exposure defined by agent; no appropriate exposure measurements

ETS Lung 1465 0 0 67 156

Coal tars NMSC 489 800 877 602 475 433 402

Radon Lung 220 379 411 341 317 309 190

Solar radiation NMSC 1749 3069 3279 2552 2030 1503 163

Occupational circumstances, no specified carcinogen

Painters Bladder, Lung, Stomach

461 640 639 481 383 347 321

Shift work Breast 1649 3062 3848 2134 1178 194 0

Welders Lung 189 140 63 105 83 76 70

Carcinogens for which exposure standards can be set

Arsenic Lung 128 92 47 92 88 87 87

Asbestos Larynx, Lung Mesothelioma, Stomach 4281 2759 2864 2785 2689 2626 2307

Diesel Bladder, Lung 380 406 399 451 412 374 34

Silica Lung 837 794 442 102 49 21 10

Strong acids Larynx, Lung 122 39 7 19 12 10 12

TCDD (Dioxins) Lung, NHL, STS286 123 30 22 8 5 6

Tetrachloro-ethylene

Cervix, NHL, Oesophagus139 135 119 123 118 117 119

Total 12050 12327 12938 9812 7944 6064 3705

Monitoring success…

• The only practicable approach is to monitor exposure levels

• No reduction in cancer levels until 2030 at earliest (for solid tumours)

• After 2030…• Use achieved exposed numbers/proportions exposed

at new exposure levels in same (target setting) forecast model to get achieved AF

• Apply achieved AF to same (2005 based) cancer projections to get achieved attributable numbers

• Do not apply achieved AF to real 2030 cancer numbers

Uncertainties and the impact on the burden estimation

Source of Uncertainty Potential impact on burden estimate

Exclusion of IARC group 2B and unknown carcinogens e.g. for electrical workers and leukaemia

↓

Inappropriate choice of source study for risk estimate

↑↓

Imprecision in source risk estimate ↑↓

Source risk estimate from study of highly exposed workers applied to lower exposed target population

↑

Risk estimate biased down by healthy worker effect, exposure misclassification in both study and reference population

↓

Inaccurate latency/risk exposure period, e.g. most recent 20 years used for leukaemia, up to 50 years solid tumours

↓

Effect of unmeasured confounders ↑↓

Unknown proportion exposed at different levels ↑↓

Summary…

• Currently about 8000 deaths and 14000 cancer cases due to past work

• Most deaths from lung cancer, mesothelioma and breast cancer

• Most deaths associated with the construction industry

• Future burden could be much lower with appropriate interventions

• Respirable crystalline silica – we need better compliance (and a lower limit)

• Best interventions differ by agent• Monitoring exposure is the best way to track

progress